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Processing 2 added doc-base files...
Registering documents with scrollkeeper...
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Setting up libqt4-help:amd64 (4:4.8.4+dfsg-0ubuntu18.1) ...
Setting up libqt4-scripttools:amd64 (4:4.8.4+dfsg-0ubuntu18.1) ...
Setting up libqt4-test:amd64 (4:4.8.4+dfsg-0ubuntu18.1) ...
Setting up libqtassistantclient4:amd64 (4.6.3-6) ...
Setting up libjs-underscore (1.4.4-2ubuntu1) ...
Setting up libqscintilla2-l10n (2.7.2-1build1) ...
Setting up libqscintilla2-9 (2.7.2-1build1) ...
Setting up mercurial-common (2.6.3-1) ...
Setting up mercurial (2.6.3-1) ...
Use of uninitialized value $reply in scalar chomp at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 66.
Use of uninitialized value $reply in concatenation (.) or string at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 67.
Use of uninitialized value $reply in split at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 68.
Use of uninitialized value $reply in scalar chomp at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 66.
Use of uninitialized value $reply in concatenation (.) or string at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 67.
Use of uninitialized value $reply in split at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 68.
Use of uninitialized value $reply in scalar chomp at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 66.
Use of uninitialized value $reply in concatenation (.) or string at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 67.
Use of uninitialized value $reply in split at /usr/share/perl5/Debconf/FrontEnd/Passthrough.pm line 68.

Creating config file /etc/mercurial/hgrc.d/hgext.rc with new version
dpkg: error processing mercurial (--configure):
 subprocess installed post-installation script returned error exit status 128